Super UPS from South Africa

It's public knowledge that South Africa's sole electric company is battling to keep up with demand. You only have to look at my UPS performance summary to appreciate the amount of brownouts we experience in our area of Margate.
Sometimes the brownouts last up to eight hours or more. As a result, I have collected all manner of uninterruptible power supplies which are linked to all the computers scattered around my house. This ensures Iï¿½m not left in the dark halfway through a game or a spreadsheet I spent the last hour compiling. Those of you who have experienced this know how infuriating power loss can be.

Comments

Great. I'm at work so just had time to scan the article and look at pics. This will get a detailed reading from me later! I'm already thinking about a new project for next winter. (heavy snowfall sometimes knocks out our power)

Been looking for something like this, having a laptop is nice because of the battery, but mine only lasts like 2-3hrs, having a much bigger battery would make it much more awesome in the event of a power outage.

*if* that is, as it appears to me, a car battery (or a pair of them), I sincerely hope you have the area well ventilated. They can and do give off hydrogen gas, which, if allowed to accumulate, is highly explosive. Let me reword that, it's explosive in any quantity but DANGEROUS if allowed to accumulate. Oh, the humanity, etc.

I admit I scanned the article rather than giving it a detailed reading, so if this is covered in there I apologize for redundancy.

You use sealed lead acid batteries, no hydrogen venting it is all internally re-absorbed.

This is the right track for serious backup. (do you have a basement? does it have a sump pump? Does the pump run during big storms?)

We were building these for field equipment when I was working in oil and gas. We bought lightning arrestors/line filters from one source (I wish that I could remember because they were real good), inverters from another and battery charging/monitoring stuff from a third.
We had a small Li ion battery to back up the electronics and three or four big ass deep draw sealed lead acid batteries for power.
They are big and don't look pretty, but they were 1/4 the price of pre-built units and worked very well.

*if* that is, as it appears to me, a car battery (or a pair of them), I sincerely hope you have the area well ventilated. They can and do give off hydrogen gas, which, if allowed to accumulate, is highly explosive. Let me reword that, it's explosive in any quantity but DANGEROUS if allowed to accumulate. Oh, the humanity, etc.

I admit I scanned the article rather than giving it a detailed reading, so if this is covered in there I apologize for redundancy.

It is not advisable to run any laser printers on UPS or inverters unless they are of an on-line type and have been specifically rated to handle the current required to heat the element. If you are running a laser printer directly off batteries you are likely to blow your unit. I ran the laser printer off batteries only once, and only as a means to push the inverter to its maximum in order to gauge its performance.

I would never have thought of this... My laser printer dims the lights in the room, so I can believe it.

Well as I hinted in the beginning of my article, the inevitable is happening and the state owned power stations we have are not able to keep up with demand. At the moment they are load sharing, where they shut down entire grids for 3-5 hours so they can rout sufficient power to the remaining grids. These are rotated so everybody gets a turn.

This electricity supply interruption is sending my folding stats to hell, but the good news is I finally get a chance to field test my UPS

I shut down all the other gizmos and peripherals bar the router and the 2 PC's and LCD monitors. (Since writing the article the CRT has also been upgraded to a Wide Screen 19") The UPS has been running both PC's for the last 4 1/2 hours, both of which are still folding so are using 100% of the CPU and my kid has been gaming for about an hour and there is as yet no signs of the batteries giving out.

I thought I would get this post out before it gives up the ghost and will let you guys know how how long it took before the final death knell

power restored before the UPS gave out. There goes my field test.
However 5 hours 20 minutes is nothing to sneeze at in my books. The Inverter had begun to beep indicating low battery and with the test I ran the last time with it on full load it beeped for about half an hour and then died. So I guess it had another 15 minutes of life left in it max.

We have 10 computers at the office all on separate UPS's. we also have about 10 dead UPS's (sealed batteries are dead) laying about the office.

Is there any reason why we shouldn't buy a 300 amp/hour deep cycle battery, similar to what is used on solar installations, and take those 10 cheap UPS's with dead batteries, pull out the batteries and wire them all to the deep cycle battery. Then put a charger on the deep cycle battery. Shouldn't the deep cycle battery run all those UPS's for a good amount of time in case of a power outage?

We have 10 computers at the office all on separate UPS's. we also have about 10 dead UPS's (sealed batteries are dead) laying about the office.

Is there any reason why we shouldn't buy a 300 amp/hour deep cycle battery, similar to what is used on solar installations, and take those 10 cheap UPS's with dead batteries, pull out the batteries and wire them all to the deep cycle battery. Then put a charger on the deep cycle battery. Shouldn't the deep cycle battery run all those UPS's for a good amount of time in case of a power outage?

Been looking around the Internet and wondering why this isn't done.

I bought a UPS from an auction, paid a US dollar for it. Dead battery. Went to local store (Walmart) and bought 6 12v lawn mower batterys. Hooked them up in parrellel (UPS took 12v) and was able to run from it for 3 hours at a time when the power went out. It finally died after 2 years of service... right after I got a laser printer, I guess I went over the max draw, didn't realise how much they pulled.

We have 10 computers at the office all on separate UPS's. we also have about 10 dead UPS's (sealed batteries are dead) laying about the office.

Is there any reason why we shouldn't buy a 300 amp/hour deep cycle battery, similar to what is used on solar installations, and take those 10 cheap UPS's with dead batteries, pull out the batteries and wire them all to the deep cycle battery. Then put a charger on the deep cycle battery. Shouldn't the deep cycle battery run all those UPS's for a good amount of time in case of a power outage?

Been looking around the Internet and wondering why this isn't done.

I think that'd put you on the right track provided your UPSs and the charger could handle the 300 amp/hour battery.

Mike,
This is an excellent article and helps me allot with a similar problem I have. I am curious though in that if, 24V (i.e. in your case, 2 times 12 batteries wired in series) provided you with approx 2 hours, what do you speculate would happen if you added additional 24 v batteries in series? Would you have in effect extended the up time by almost double? Who would the outcome be if you added another 24V but in this time in parallel?
Cheers
Mark

Mike,
This is an excellent article and helps me allot with a similar problem I have. I am curious though in that if, 24V (i.e. in your case, 2 times 12 batteries wired in series) provided you with approx 2 hours, what do you speculate would happen if you added additional 24 v batteries in series? Would you have in effect extended the up time by almost double? Who would the outcome be if you added another 24V but in this time in parallel?
Cheers
Mark

Adding in series would up the voltage, a bad thing if the UPS's voltage regulator couldn't handle the extra voltage.

If you added more batteries in parellel (I think he mentions that in the article) it would increase the up time. 2 batteries last 2 hours, 4 batteries would last almost 4 hours, 6 batteries would last about 5.5 hours. You lose a small fraction each time you add batteries because of the added resistance of the extra wiring and the batteries' internal resistance.

I live in the Florida Keys, and 15 years ago our power situation was only a little better than South Africa. Daily, hour long outages were common. It has improved a lot, though we're still at the end of a long extension cord.

I was part of a ISP startup that ran on a shoestring budget and the UPS being one of the places that we saved the $$$ to put into good modems. We used an 800kva UPS with dead batteries and two group 27 Lifeline sealed Lead Acid batteries ( series, for 24V ). We removed the dead batteries from the UPS, cut a small hole in the side of the case and added our own 4ga. battery cable extensions.

After using it for a bit, it seemed that the UPS's internal battery charger got confused by the additional capacity of the larger batteries ( though it's possible that it had an issue the whole time, and that's why the original batteries were dead ) and didn't fully recharge the batteries, so I added an external float charger to keep the batteries at the correct voltage.

It worked well, gave us something like 3+ hours of runtime ( enough for someone to run down and start the generator) and cost us about $425 ( $200 each for the batteries, $25 for the float charger- the UPS was free ).

After the ISP went under, it came to my house to run my entertainment center through hurricane Georges.

If you added more batteries in parellel (I think he mentions that in the article) it would increase the up time. 2 batteries last 2 hours, 4 batteries would last almost 4 hours, 6 batteries would last about 5.5 hours. You lose a small fraction each time you add batteries because of the added resistance of the extra wiring and the batteries' internal resistance.

You're right about it being a bad idea to add more batteries in series, but actually, I think you'll get BETTER than three times the runtime by tripling the number of batteries. ( Pairs of batteries in parallel, that is two batteries in series for 24V, and those pairs each in parallel )

like this:

-[__UPS___]-

-[bat]-[bat]-

-[bat]-[bat]-

-[bat]-[bat]-

Battery or wiring resistance should only go down since the pairs ( two batteries in series ) are connected in parallel. The one part of the string where the current is flowing through single wires shouldn't have any more current than a single pair.

Besides, if you're getting significant resistance from the wiring, it's too small, at least at this scale.

Next, battery capacity goes UP when you lower the demand. ( I can't post a link, I'm too new. Look up "Peukert's Law" on Wikipedia to learn more and see the equations...)

The numbers below are made up, but they illustrate the principal. The actual equation will vary a lot with battery chemistry and construction. Flooded lead acid batteries are affected by this more than sealed lead acid batteries.

Batteries are normally rated for a 20 hour discharge. That is to say a 100Ah battery is rated to deliver 5A for 20 hours when tested to full discharge.

If you pull the power faster, you get less power out of the battery. If you drain the battery in 10 hours, you might only get 85Ah. If you did it in 5 hours, you might get just 70Ah. If you did it in 1 hour, you might get as little as 50Ah, or just half the energy you'd get in a 20 hour discharge.

Let's apply this to the UPS example. Let's say your UPS draws 50A from a battery to run your stuff.

If you use the 100Ah battery from my example above, a 50A draw will drain the battery in just an hour, since the high current draw will make the battery able to deliver just 50Ah.

However, if you triple the number of batteries ( thus tripling the rated capacity of the batteries ) you get more than 3 times the runtime. Since the drain rate is slower ( at least three times the single runtime...) each battery delivers it's power more slowly and you'll get more out of each battery, perhaps 65Ah. 65Ah time three ( the number of batteries ) is 205Ah. That's a runtime of a little over 4 hours.

So a tripling of the batteries might quadruple the runtime, more or less.

Any thoughts on doing the accumulation/buffering on the DC side of the PC-PSU (to avoid the extra up-down conversion)? If the device in question is a fairly low-power headless server which could be made from notebook parts? On the surface it seems relatively simple (notebook vendors do it all the time), which means it's probably ridiculously difficult.

(I know, this is for a setup with only a few devices in need of backup, which is not what the article was about, but since we're on the topic of UPSs ...)